Estrogens are versatile hormones, which are essential for various physiological functions in women. Reduced estrogen production from the ovaries due to surgical resection, ablative therapy, or menopause leads to various physiological consequences in women. Although hormone replacement therapy is able to compensate for the loss of estrogen production, delivery through pharmacological means results in consistently high serum concentrations. Clinical complications include increased incidence of heart disease and cancer. Accordingly, there is a need for new methods and techniques for delivering estrogen.